To conduct the experiment, which appears online in Springer publishing's Experimental Brain Research journal, Dr. James Schirillo and co-author Kelsey Blackburn took photos of 10 male and female faces. The photos were cast in gray-scale, the poor man's Photoshop. Very art house.

Schirillo and Blackburn used those pictures to create a second series of mirrored images in which the right side of the face appeared to be the left side, and vice versa.

They then asked 37 male and female college students to rate the pleasantness of both sides of the faces, based on the images in their arsenal.

The results were clear: People showed a strong preference for left-cheek images.

The really interesting thing, though, is that it didn't matter whether the side in question was the subject's real life left-side or if it was a right-side that had been flipped to the left when the image was mirrored. Participants rated as "more pleasant" the side that appeared to be on the left in either case.

In addition to using participants' own rankings, the researchers also examined their pupil size when rating the faces. Since pupils dilate when taking in "interesting" (or pleasing) images, it was expected that they would grow larger when subjects were looking at the sides they found most pleasant. The results were as expected: Pupils swelled when participants studied what appeared to be the left side of a face and shrunk when they looked at the right.

According to Blackburn and Schirillo, the preference for left profiles likely stems from the fact that individuals' left cheeks tend to broadcast "a greater intensity of emotion, which observers find more aesthetically pleasing."

They go on to speculate that the left side is more emotive because the right side of the brain (which controls the left side of the face) controls emotion.

An informal poll of me looking in a mirror right now has confirmed that these findings are definitely true.

(For what it's worth, there's some vague historical evidence too: portraits by western artists more often depict their subjects in a left side profile than a right.)